1. Field of the Invention
This invention relates to apparatus and accompanying methods for use in a film to video transfer system for achieving automatic color balancing of color photographic images for subsequent display on a color monitor.
2. Description of the Prior Art
Traditionally, images have been stored and displayed in optical form. For example, photography is one commonly used method of capturing and subsequently displaying an image. Through photography, an image is captured through photo-chemical interactions occurring in a light sensitive medium, e.g. film, whenever that medium is exposed to light emanating from a desired scene, with the resulting image being depicted either as a developed photographic print or as a transparency, the latter forming a part of what is commonly referred to as a slide. With either prints or slides, the image is fixed by a pattern of color dyes dictated by the coloration of the captured image that has been captured on the film. Though photographic processes currently provide very high quality images, photography can be a somewhat tedious and problematic process, both in terms of properly exposing a piece of film and in terms of correctly developing that film to yield a proper optical depiction of the image. Moreover, a finite amount of time is required to transform an exposed piece of film, such as by processing it, into a visible image, such as a transparency, a color negative and/or a color print.
In addition, photographic images tend to be clumsy to display, particularly to relatively large groups such as those that might fill a classroom or an auditorium. In particular, available enlarging equipment limits the size of a color print. Moreover, greatly enlarged prints, due to their size, are frequently cumbersome to handle. Furthermore, greatly enlarged prints tend to be very expensive owing to the paper and enlarging equipment needed to produce the print. For those reasons, transparencies are often used in lieu of prints. Transparencies, in this case slides, are merely inserted in a desired order into a suitable carousel which, in turn, is placed into a slide projector. The projector successively projects light through each selected slide onto a suitable screen which is positioned some distance away from the projector. The distance between the screen and the projector dictates the size of the resulting displayed image. While slides, in many instances, provide a far more convenient way of displaying images than through prints, slides have various drawbacks that tend t limit their utility.
First, slides are also cumbersome to handle. Slides must be first be arranged into a desired order before they are inserted into a carousel. If for some reason the carousel is mishandled, e.g. dropped, and the slides separate from the carousel, the slides must again be placed into the proper order. This is time consuming. Furthermore, slides are relatively fragile. Inasmuch as light is projected through a transparency that forms part of the slide, the slide, though containing a protective frame peripherally situated around the transparency, must be carefully handled to prevent scratches or tears to the transparency which, in turn, would corrupt the resulting image. In addition, slides are usually shown in a darkened room which, as such, is generally not conducive to maintaining the attention of the viewers that are present there. In addition, the need for available projection equipment, including a suitably large screen, tends to limit the location at which slides can be shown.
In view of the drawbacks associated with photographically generated images, whether through prints or transparencies, the art is increasingly turning to video as a convenient way of capturing and subsequently displaying images. Owing to the proliferation of television and video display terminals as a communication media, viewers over the past several years are becoming increasingly accustomed to viewing a video image and generally prefer seeing a video image rather than an image projected from a slide. Moreover, since color monitors and video tape recorders are becoming rather ubiquitous, video images can be easily displayed at nearly any location. These cassettes are highly transportable, relatively inexpensive, can store an extraordinarily large number of different images, are much less susceptible to damage than slides and, owing to the ready transportability of a video cassette player and monitor, can be displayed nearly anywhere. Hence, for these reasons, video images that have been recorded on video cassettes are rapidly displacing slides by finding increasing use in educational, training, sales and many other environments and thereby becoming a preferred medium of choice.
Presently, a great body of visual information exists in photographic form, i.e. stored on developed film, either on slides, transparencies or other photographic formats. To display this information visually on a monitor, the information needs to be electronically converted into a suitable video form, such as an NTSC (National Television System Committee) composite video signal or separate red, green and blue (RGB) signals, for use with an available color monitor. While, at first blush, one would think that the conversion would simply involve electronically scanning a photographically produced image with a video camera and then storing the resulting video image. Unfortunately, this simplistic technique produces inadequate results.
Although photography provides an individual with an exceptionally wide latitude in capturing an image, oftentimes the actual image that is captured on film (negatives or slides) does not accurately depict an original scene. This can occur for any one of various reasons, such as illustratively because the exposure, lens aperture and/or shutter speed, is incorrect which results in an over- or under-exposure, the type of lighting, i.e. tungsten, fluorescent or sunlight, is not appropriate for the specific film being used, or the film is old and as a result has a reduced sensitivity. Generally, with a photographically recorded image, color balancing is used during a developing process in an effort to correct most deficiencies that reside in the image. Color balancing involves optically changing the coloration in an image, as originally captured on film, in a deliberate fashion.
The art has recognized that if a subsequent depiction of a photographic image on an output media is to be as faithful a reproduction of an original scene as possible, then not only must chromatic response differences that occur between an input media that captured the image and the output media be removed through color balancing but also deficiencies, to the extent they are correctable, that occur in the photographic image itself, must also be corrected as well. For example, teachings along these lines appear in U.S. Pat. No. 4,500,919 (issued to W. F. Schreiber on Feb. 19, 1985 and henceforth referred to herein as the '919 patent) in the context of use within a color editing system that generates appropriately engraved color separated printing cylinders for use a gravure printing press or the like to subsequently reproduce a color photographic image. Similar teachings appear in U.S. Pat. No. 4,364,084 (issued to T. Akimoto et al on Dec. 14, 1982 and henceforth referred to herein as the '084 patent) in conjunction with a system for transferring images on developed color film to photographic paper.
Therefore, a goal of any film to video transfer system must be end to end fidelity. Specifically, if the system is to produce a proper video depiction of a scene that has been photographically captured, then that scene must be reproduced as sharply and as perfectly as possible in video form even though the underlying photographic image itself may be somewhat defective. Hence, if the photographic image is defective, the deficiencies existing therein must be corrected prior to the image being stored in video form for subsequent display. For that reason, a film to video transfer system must employ color balancing.
Unfortunately, color balancing techniques generally known in the art often provide inadequate results. Specifically, in most instances, color balancing techniques known in the art for use in image transfer systems usually rely on some form of manual operator intervention in order to achieve a suitable color balance. In this regard, some known color balancing techniques, such as that disclosed in U.S. Pat. No. 4,583,186 (issued to R. C. Davis et al on Apr. 15, 1986) and U.S. Pat. No. 4,310,848 (issued to W. D. Carter et al on Jan. 12, 1982), rely on displaying a scanned photographed image and then requiring an operator to manually adjust the coloration of the displayed image prior to that image being printed. Other known color balancing techniques, such as those exemplified by the teachings in the '919 patent, the '084 patent and in U.S. Pat. No. 4,676,628 (issued to Asbury on June 30, 1987) and U.S. Pat. No. 3,972,066 (issued to Seki et al on July 27, 1976) attempt to first color balance a scanned photographic image in a pre-determined fashion and display a resulting color balanced image on a color monitor to an operator who is then free to manually change the coloration of any portion of the image, if necessary and as desired, to produce a proper depiction of an original scene. Unfortunately, in any of these prior art techniques, time is consumed whenever an operator intervenes to adjust the color or even to just inspect the image. This, in turn, disadvantageously decreases the throughput of the image transfer system that uses such a color balancing technique. Since the time available for operator intervention is often quite limited, color balance techniques known in the art have not always yielded satisfactory results.
Hence, while recognizing the need to employ some form of color balancing, the art has thusfar failed to provide a technique for use in an image transfer system, and particularly in a film to video transfer system, that automatically and properly color balances an image while generally eliminating or, at the very least, substantially reducing the need for operator intervention.
Therefore, a need currently exists in the art for apparatus and accompanying methods for use therein that, to the extent possible, automatically balances colors in a film to video transfer system in order to provide a faithful reproduction of an original scene. Not only should this apparatus automatically balance the colors based upon differences in chromatic response between film and video but also this apparatus should be able to substantially correct for deficiencies that occur in a photographed image itself.